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<!-- Changed by: Greg Ewing, 9-Dec-1997 -->
<h1>class <tt>MessageHandler </tt></h1>
<p>MessageHandler is an abstract base class for objects which
participate in the message delivery hierarchy. The message delivery
mechanism is used to handle events such as keystrokes and menu commands
which are not directed at a particular point on the screen. See <a href="event_handling.html">Event Handling</a> for more
information.</p>
<h2>Methods</h2>
<dl style="margin-left: 40px;">
<dt><tt>handle(msg_name, ...)</tt></dt>
<dd>If there is a method with the same name as the message,
calls it
with the message arguments. Otherwise, passes the message to the next
handler.<br><br></dd><dt style="font-family: monospace;">handle_here(msg_name, ...)</dt><dd>If there is a method with the same name as the message,
calls it
with the message arguments. Otherwise, does nothing.<br><br></dd><dt style="font-family: monospace;">handle_event(event)</dt><dd>Equivalent to <span style="font-family: monospace;">handle(event.kind, event)</span>.<br><br></dd><dt style="font-family: monospace;">handle_event_here(event)</dt><dd>Equivalent to <span style="font-family: monospace;">handle_here(event.kind, event)</span>.<br><br></dd><dt style="font-family: monospace;">pass_to_next_handler(msg_name, ...)</dt><dd>Calls the <span style="font-family: monospace;">handle()</span> method of the next message handler, if any.<br><br></dd><dt style="font-family: monospace;">pass_event_to_next_handler(event)</dt><dd>Equivalent to <span style="font-family: monospace;">pass_to_next_handler(event.kind, event)</span>.<br></dd>
<dt><tt>next_handler()</tt></dt>
<dd>Returns the object, if any, to which messages not handled
by this object should be passed up.</dd>
</dl>
<h2>Abstract Methods</h2>
<blockquote>
<dl>

<dt><tt>key_down(</tt><i>event</i><tt>)<br>
</tt></dt>
<dt><tt>key_up(</tt><i>event</i><tt>)</tt></dt>
<dd>These methods are called in response to keyboard events.
The default implementations pass the event to the next handler.<br><br>
</dd>
<dt><tt>setup_menus(menu_state)</tt></dt>
<dd>During the menu setup phase of menu command processing,
this method
is called for all handlers along the message path in reverse order,
i.e.
from the Application down to the current target. MessageHandlers should
use
this method to enable and otherwise configure any menu items that they
respond
to and which are currently valid.&nbsp;See <a href="menu_setup.html">Menu Setup</a> for more
information.</dd>
</dl>
<dl>
</dl>
</blockquote>
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